1. Field of the Invention
The present invention generally relates to multifocal ophthalmic lenses. More specifically, the present invention provides improved progressive addition lenses (PALs) having one or more discontinuities.
2. Background Art
The only technique of conventional PALs to merge or connect surface segments having different curvatures or average optical power is the use of blend zones. In general, blend zones comprise a continuous change in curvature or average power in areas of a PAL surface where a divergence of sagittal and tangential curvatures exists. By merging areas of different curvature in this way, unwanted astigmatism on the surface of the PAL is introduced. Conventional PAL design involves optimizing the distribution of this unwanted astigmatism to minimize its effect on the visual performance of the lens. Accordingly, what is needed is a multifocal ophthalmic lens design that provides another technique for merging or connecting regions having different curvatures or average power so as to provide an improved PAL design.